Oh thats whzDifferences between the full and beta:
1.Warcraft 3 Beta: Only Multiplayer (Battle.net) is available. The game is still buggy. I heard that when I watched the gameplay video by Retera, the game freezes when you play as Undead or Night Elf.
2.Warcraft 3 Demo: You can only play 3 missions of Orc (Exodus of the Horde, it's also available on The Frozen Throne).
Choose wisely. There are some limitations between Beta and Demo.